Selective hydrogenation catalyst for pyrolysis gasoline

ABSTRACT

The present invention is related to a selective hydrogenation catalyst for pyrolysis gasoline, wherein the catalyst mainly consists of a support of δ, α mixed alumina covered by palladium as active component, promoter as co-active component and alkali metal and/or alkaline-earth metal. Said palladium is distributed like egg shell on the support surface. Said support has 0.5˜0.9 ml/g of specific pore volume, wherein 40˜200 Å pores account for more than 85% of the total pore volume, preferably 100˜200 Å pore volume accounts for 65%˜80% of the said total pore volume in catalyst support. The specific surface area is about 70˜140 m 2 /g , and a crystal type in the alumina support is about 0.1˜5% based on the weight percentage of δ, α mixed alumina support, said catalyst contains promoter having selected from a group of the VIB or IB elements in the periodical table of elements. The ratio of promoter and palladium by weight is about 0.2˜2:1. The alkali metal and/or alkaline-earth metal is added in amount of 0.05˜2.0 wt %.

[0001] This invention involves a selective hydrogenation catalyst forpyrolysis gasoline and the preparation thereof.

THE BACKGROUND OF THE INVENTION

[0002] At present, the selective hydrogenation catalyst for industrialpyrolysis gasoline is still taking palladium-based catalyst as the main.There is also the palladium catalyst added with the catalyst promoter.Most of the co-activating component is elements of IA group in theperiodical table of elements. For those materials of pyrolysis gasolinewith high impurity, the noble metal nickel catalyst has been used for along time. Because of its slow starting temperature, high hydrogenationactivation, large precession material quantity and long lifetime etc,the palladium-based catalyst is obviously superior to catalyst of nickelgroup, for example, as disclosed in U.S. Pat. No. 4,410,455. But whenpyrolysis gasoline contains high diene and the impurities such asarsenic and colloid, many of the industrialized palladium-basedcatalysts are difficult to operation with stability and for a long timein designed space velocity. It frequently occurs that even though thedesigned space velocity of catalyst can reach 4.7 h⁻¹ during theprocedure of fresh feed-in, but it only can operate with a reduced spacevelocity of 2.8 h⁻¹ due to too heavy feed-in and too much impurity.

[0003] In order to overcome the deficiency of the prior arts, the objectof the present invention is to provide a series of palladium-basedhydrogenation catalysts that are adaptive for raw material with highimpurity and suitable for operation under high space velocity. Anotherobject of the present invention is to provide a preparation method of aseries of palladium-based hydrogenation catalysts.

THE SUMMARY OF THE INVENTION

[0004] According to the present invention, a selective hydrogenationcatalyst for pyrolysis gasoline is provided, wherein the catalyst mainlyconsists of a support of δ, α mixed alumina covered by palladium asactive component and alkali metal and/or alkaline-earth metal. Thepalladium is distributed like egg shell on the support surface. And saidsupport has 0.5˜0.9 ml/g of specific pore volume, wherein 40˜200 Å poresaccount for more than 85% of the total pore volume, preferably, 100˜200Å pore volume accounts for 65%˜80% of the said total pore volume incatalyst support. The specific surface area is about 70˜140 m²/g. And αcrystal type in the alumina support is about 0.1˜5% based on the weightpercentage of δ, α mixed alumina support. Said catalyst comprisespalladium in amount of 0.05˜0.4 wt %, alkali metal and/or alkaline-earthmetal in amount of 0.05˜2.0 wt %.

[0005] The present invention is also related to a selectivehydrogenation catalyst for pyrolysis gasoline, wherein the catalystmainly consists of a support of δ, α mixed alumina covered by palladiumas active component, promoter as co-active component and alkali metaland/or alkaline-earth metal. Said palladium is distributed like eggshell on the support surface. Said support has 0.5˜0.9 ml/g of specificpore volume, wherein 40˜200 Å pores account for more than 85% of thetotal pore volume, preferably 100˜200 Å pore volume accounts for 65%˜80%of the said total pore volume in catalyst support. The specific surfacearea is about 70˜140 m²/g, and a crystal type in the alumina support isabout 0.1˜5% based on the weight percentage of δ, α mixed aluminasupport, said catalyst containing promoter having selected one from agroup of the VIB or IB elements in the periodical table of elements. Theratio of promoter and palladium by weight is about 0.2˜2:1. The alkalimetal and/or alkaline-earth metal is added in amount of 0.05˜2.0 wt %.

[0006] According to the invention, the shape of the said catalyst can beeither of mechanical punching or of clover or cylinder bar. The shape ofsupport grain does not influence the application of this invention.

[0007] The present catalyst is adaptive for hydrogenation of totalfraction of pyrolysis gasoline and C₆˜C₈ intermediate fraction petrol.

[0008] The preparation method of catalyst of this invention is used bythe method that is known to the person skilled in the arts. In general,that is to say it is the same to the immersion technology for makingordinary lamella catalyst. Therefore, the present invention is toprovide a method for preparation of a selective hydrogenation catalystfor pyrolysis gasoline comprising the following steps:

[0009] (i) preparing aqueous solution containing palladium and alkalimetal and/or alkaline-earth metal in amount of 0.05˜2.0 wt %, the pH ofsaid solution being less than 4;

[0010] (ii) immersing δ, α mixed Al₂O₃support in said solution at100-150 ° C.;

[0011] (iii) sintering the immersed support at about 380-500° C. to geta catalyst.

[0012] In the method of the invention, a promoter is applied to formimmersion solution. Said promoter is selected from a group of the VIB orIB elements in the periodical table of elements.

[0013] In addition, ratio of promoter and palladium by weight in thepresent method is defined to 0.2˜2:1.

[0014] In another words, Firstly, solution which can be mutual-solublewith the immersion liquid (for example the deionized water) is used toimmerse the pre-immersed support, then the pre-immersed δ, α mixedalumina support is immersed with salt solution having active componentsuch as palladium. After washing, drying and sintering, the immersedsupport will become a final product of oxide-type catalyst. The catalystproduct can be used after the deoxidization by putting in hydrogen inreactor.

[0015] The promoter in the invention can form a complex with palladium.The formation of such a complex is beneficial to the even distributionof palladium grains, and to improve and increase the utilization factorof palladium, and to reduce the loss of palladium and extend thelifetime of catalyst. The alkali metals can change the acid-base statusof support surface, which is beneficial to reduce sedimentation ofcolloid and carbon in hydrogenation period. The pores are evenlydistributed, which has the function of reducing the inner diffusionresistance. The larger specific pore volume is beneficial to thematerial with a bigger procession quantity and higher impurity contents.In combination of the above-mentioned factors, the catalyst of thisinvention is especially adaptive for the procession of material withhigh impurity contents as well as for the hydrogenation under higherspace velocity. For example, the procession of total fraction pyrolysisgasoline of colloid will be ≦60 mg/100 mi, diene value ≦40 g iodin/100 gpetrol, especially under the space velocity of 4.0˜6.0 h⁻¹ (fresh oil),it can carry out the hydrogenation to the C₆˜C₈ medium petrol.

[0016] The catalyst can be prepared classically by the shell layerimmersion technology as known by the skilled in the arts. During thepreparation, the elements as promoter selected from a group of the VIB,IB, IA and IIA in the Periodical Table of Elements are applied. Theiroxides, hydroxides and organic and inorganic salts of the promoterelements are preferable to be used in the present invention. Thesesubstances are added to fully dissolve to make immersion solution. Inaddition, said support may be pre-immersed with solution that can mixwith immersion solution each other.

[0017] The advantages of this invention are that the large quantity ofmaterials can be treated (for C₆˜C₈ medium fraction petrol, the spacevelocity can reach 4.0˜6.0 h⁻¹ when the fresh petrol is calculated); forthe treatment of material with high impurities, the hydrogenationactivity is high with good selectivity. The chemical stability and thethermal stability are much better during the long period operation. Thesol performance is good and the carbon quantity is low. The catalyst haslong lifetime and the preparation thereof is simple.

[0018] The foregoing and other advantages of the invention will appearfrom the following description. These embodiments do not represent thefull scope of the invention. Thus, the claim should be looked to inorder to judge the scope of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS EXAMPLE 1

[0019] 0.2 ml of Cu(CH₃COO)₂ solution (0.03 gCu/ml) was mixed with 0.1ml of Mg(NO₃)₂ solution (0.12 g Mg/ml) and 0.6 ml of H₂PdCl₄ solution(0.1 g Pd/ml) to obtain 20 ml of immersion solution with pH value ofless than 4. 20 g of δ, α mixed Al₂O₃ support was pre-immersed with thedeionized water. Then the support was immersed in 20 ml of saidimmersion solution for about 30 minutes at 100° C. The treated supportwas filtered and separated and washed by distilled water until no Cl⁻ion was detected in wash water. The pH of remaining solution will not beequal to 4.0. The immersed support was dried in about 150° C. andsintered at 380° C. to get a oxidized catalyst of this invention. Theexternal appearance of catalyst is filbert and likes a clover bar inlight brown color. Its specification can be φ2.8˜3.2×3˜10 mm. Thephysical features of catalyst are shown in table 1.

EXAMPLE 2

[0020] The same procedure was repeated with Example 1 except that 0.1 mlof AgNO₃ solution (0.005 g Ag/ml) was mixed with 0.2 ml of Na₂CO₃solution (0.17 g Na/ml) and 0.8 ml of H₂PdCl₄ solution (0.1 g Pd/ml) toobtain activated immersion solution. After pre-immersed with thedistilled water, 20 g of δ, α mixed Al₂O₃ support was immersed with saidimmersion solution. The immersed support was dried in about 120° C. andsintered at 400° C. to get a catalyst with physical features indicatedin Table 1.

EXAMPLE 3

[0021] The same procedure was repeated with Example 1 except that 0.3 gof MoO₃ and 0.33 g K₂CO₃ were mixed with distilled water to be fullydissolved. 0.1 ml Of Ba(NO₃)₂ (0.28 g Ba/ml) solution was mixed with 0.5ml of H₂PdCl₄ solution (0.1 g Pd/ml) to obtain activated immersionsolution. After pre-immersed with the distilled water, 20 g of δ, αmixed Al₂O₃ support was immersed with said immersion solution. Theimmersed support was dried in about 100° C. and sintered at 400° C. toget a catalyst with physical features indicated in Table 1.

EXAMPLE 4

[0022] The same procedure was repeated with Example 1 except that 0.95ml of Cu(CH₃COO)₂solution (0.03 gCu/ml) was mixed with 0.4 ml of LiNO₃solution (0.46 g Li/ml) and 0.6 ml of H₂PdCl₄ solution (0.1 g Pd/ml) toobtain activated immersion solution. After pre-immersed with thedistilled water, 20 g of δ, α mixed Al₂O₃ support was immersed with saidimmersion solution. The immersed support was dried in about 100° C. andsintered at 400° C. to get a catalyst with physical features indicatedin Table 1.

EXAMPLE 5

[0023] The same procedure was repeated with Example 1 except that 0.8 mlof Cr(NO₃)₃ solution (0.5 gCr/ml) was mixed with 0.58 g Ca(OH)₂to have amixture. 0.56 g of H₂PdCl₄ solution (0.1 g Pd/ml) was added to themixture to obtain activated immersion solution. After pre-immersed withthe distilled water, 20 g support was immersed in 20 ml of saidimmersion solution for about 30 minutes at 100° C. The treated supportwas filtered and separated and washed by distilled water until no Cl⁻ion was detected in wash water. The pH of remaining solution will not beequal to 4.0. The immersed support was dried in about 150° C. andsintered at 380° C. to get a oxidized catalyst of this invention. Theexternal appearance of catalyst is filbert and likes a clover bar inlight brown color. Its specification can be φ2.8˜3.2×3˜10 mm. Thephysical features of catalyst are shown in table 1.

EXAMPLE 2

[0024] The same procedure was repeated with Example 1 except that 0.1 mlof AgNO₃ solution (0.005 g Ag/ml) was mixed with 0.2 ml of Na₂CO₃solution (0.17 g Na/ml) and 0.8 ml of H₂PdCl₄ solution (0.1 g Pd/ml) toobtain activated immersion solution. After pre-immersed with thedistilled water, 20 g of δ, α mixed Al₂O₃ support was immersed with saidimmersion solution. The immersed support was dried in about 120° C. andsintered at 400° C. to get a catalyst with physical features indicatedin Table 1.

EXAMPLE 3

[0025] The same procedure was repeated with Example 1 except that 0.3 gof MoO₃ and 0.33 g K₂CO₃ were mixed with distilled water to be fullydissolved. 0.1 ml Of Ba(NO₃)₂ (0.28 g Ba/ml) solution was mixed with 0.5ml of H₂PdCl₄ solution (0.1 g Pd/ml) to obtain activated immersionsolution. After pre-immersed with the distilled water, 20 g of δ, αmixed Al₂O₃ support was immersed with said immersion solution. Theimmersed support was dried in about 100° C. and sintered at 400° C. toget a catalyst with physical features indicated in Table 1.

EXAMPLE 4

[0026] The same procedure was repeated with Example 1 except that 0.95ml of Cu(CH₃COO)₂solution (0.03 gCu/ml) was mixed with 0.4 ml of LiNO₃solution (0.46 g Li/ml) and 0.6 ml of H₂PdCl₄ solution (0.1 g Pd/ml) toobtain activated immersion solution. After pre-immersed with thedistilled water, 20 g of δ, α mixed Al₂O₃ support was immersed with saidimmersion solution. The immersed support was dried in about 100° C. andsintered at 400° C. to get a catalyst with physical features indicatedin Table 1.

EXAMPLE 5

[0027] The same procedure was repeated with Example 1 except that 0.8 mlof Cr(NO₃)₃ solution (0.5 gCr/ml) was mixed with 0.58 g Ca(OH)₂to have amixture. 0.56 ml of H₂PdCl₄ solution (0.1 g Pd/ml) was added to themixture to obtain activated immersion solution. After pre-immersed withthe distilled water, 20 g of δ, α mixed Al₂O₃ support was immersed withsaid immersion solution. The immersed support was dried in about 110° C.and sintered at 500° C. to get a catalyst with physical featuresindicated in Table 1.

EXAMPLE 6

[0028] The same procedure was repeated with Example 1 except that 0.4 mlof LiOOCCH₃ solution (0.46 g Li/ml) was mixed with 0.56 ml of H₂PdCl₄solution (0.1 g Pd/ml) to obtain activated immersion solution. Afterpre-immersed with the distilled water, 20 g of δ, α mixed Al₂O₃ supportwas immersed with said immersion solution. The immersed support wasdried in about 110° C. and sintered at 420° C. to get a catalyst withphysical features indicated in Table 1.

Comparative Example

[0029] A single-metal Pd catalyst was prepared in accordance with thecommon method for making a Pd catalyst. The external appearance ofcatalyst is filbert with cylinder shape and in light brown color. Itsspecification is φ4×4 mm. The physical features of catalyst is shown intable 1. TABLE 1 Physical features obtained in the examples andcomparison one Com- Examples parative Item 1 2 3 4 5 6 example SupportSpecific surface 81 95 102 110 125 109 102 area m²/g Specific pore 0.620.65 0.73 0.73 0.78 0.69 0.51 volume ml/g Pore distribution: % 40˜200°A88 86 95 91 90 89 72 100˜200°A 72 69 75 70 67 71 9 Proportion of α 0.80.7 1.0 1.9 2.5 1.3 6.0 crystal type Pile intensity 0.57 0.59 0.60 0.640.58 0.61 0.79 g/ml Catalyst Pd composition 0.30 0.40 0.25 0.30 0.280.28 0.30 wt % Co-active Cu Ag Mo Cu Cr — — component wt % 0.03 0.02 1.01.4 2.0 — — 5 Alkali metal — Na K Li — Li — component wt % — 0.17 0.470.92 — 0.92 — Alkaline-earth Mg — Ba Ca — — metal 0.06 — 0.14 1.56 — —component wt %

[0030] The 1000-hours activity evaluation was carried out on 300 mlheat-insulating or adiabatic bed for the Examples1, 2, 3, 4, 5 andComparative Example 6. The evaluation results were shown in table 2.TABLE 2 Hydrogenation performances of catalyst obtained in the examplesand comparative one* examples Comparative Item 1 2 3 4 5 6 exampleOperation Conditions Temperature 45 45 45 45 45 45 50 C.° Space 5.0 4.55.5 5.5 6.0 5.0 4.0 Velocity with fresh petrol (h⁻¹) Pressure 2.8 2.82.8 2.8 2.8 2.8 2.8 MPa Ratio of 50:1 50:1 50:1 50:1 50:1 50:1 50:1hydrogen and petrol v/v Diene ratio of product after hygrogenation* gl/100 g oil iodin/100 g 200 hours 0.82 0.79 0.44 0.58 0.73 1.06 2.23 500hours 0.94 0.98 0.91 0.97 1.06 1.77 2.65 750 hours 1.06 1.02 1.02 1.081.29 1.98 2.94 1000 hours 1.32 1.08 1.18 1.22 1.68 2.05 3.02 Amount ofSol 7.8 6.9 6.5 7.0 8.7 6.7 10.6

[0031] * In the evaluation, the diene value of petrol used is 30˜40 giodin/100 g petrol, the colloid ≦60 mg/100 ml. The material petrol usedbefore 750 hours is C₆˜C₈ medium fraction of pyrolysis gasoline. In750˜1000 hours, it will be changed to all fraction material petrol ofpyrolysis gasoline.

[0032] * The measurement method for diene value in the petrol is malicacid anhydride method.

[0033] Table 3 is the comparison and evaluation result of hydrogenationperformances of catalysts in Example 4 and comparative example on the300 ml heat-insulating bed and under the high space velocity. Thematerial used in the evaluation is the C₆˜C₈ medium fraction ofpyrolysis gasoline in the evaluation. Its diene is 30˜40 g iodin /100 gpetrol and the colloid is less than 60 mg/100 ml. TABLE 3 Comparison ofhydrogenation performances of catalyst in the comparative example in thehigh space velocity Application Comparison Item example 4 exampleTemperature ° C. 50 50 Pressure MPa 2.8  2.8  Operation Hydrogen-petrolratio 50:1  50:1  Space velocity H⁻¹ with 6.0  6.0  fresh petrol Cyclicratio 3:1 3:1 Total space velocity h⁻¹ 24 24 The diene value of productafter hydrogenation gl/100 g oil 150 hours 0.61 3.28 300 hours 0.88 5.79500 hours 1.05 6.32 Amount of Sol % 6.4  9.3 

I claim:
 1. A selective hydrogenation catalyst for pyrolysis gasoline,wherein the catalyst mainly consists of a support of δ, α mixed aluminacovered by palladium and alkali metal and/or alkaline-earth metal whichare distributed like egg shell on the support surface, and said supporthaving 0.5˜0.9 ml/g of specific pore volume, wherein 40˜200 Å poresaccount for more than 85% of the total pore volume, the specific surfacearea being 70˜140 m²/g, and α crystal type in the alumina support being0.1˜5% based on the weight percentage of δ, α mixed alumina support,said catalyst comprising palladium in amount of 0.05˜0.4 wt %, alkalimetal and/or alkaline-earth metal in amount of 0.05˜2.0 wt %.
 2. Aselective hydrogenation catalyst for pyrolysis gasoline according toclaim 1 , wherein 100˜200 Å pore volume accounts for 65%˜80% of the saidtotal pore volume in catalyst support.
 3. A selective hydrogenationcatalyst for pyrolysis gasoline, wherein the catalyst mainly consists ofa support of δ, α mixed alumina covered by palladium, promoter, andalkali metal and/or alkaline-earth metal distributed like egg shell onthe support surface, said support having 0.5˜0.9 ml/g of specific porevolume, wherein 40˜200 Å pores account for more than 85% of the totalpore volume, the specific surface area being 70˜140 m²/g , and α crystaltype in the alumina support being 0.1˜5%, based on the weight percentageof δ, α mixed alumina support, said promoter being selected from a groupof the VIB or IB elements in the periodical table of elements, ratio ofpromoter and palladium by weight being 0.2˜2:1, the alkali metal and/oralkaline-earth metal being added in amount of 0.05˜2.0 wt %.
 4. Aselective hydrogenation catalyst for pyrolysis gasoline according toclaim 3 , wherein 100˜200 Å pore volume accounts for 65%˜80% of the saidtotal pore volume in catalyst support.
 5. A method for preparation of aselective hydrogenation catalyst for pyrolysis gasoline according toclaim 1 , comprising the following steps: (iv) preparing aqueoussolution containing palladium and alkali metal and/or alkaline-earthmetal in amount of 0.05˜2.0 wt %, the pH of said solution being lessthan 4; (v) immersing δ, α mixed Al₂O₃support in said solution at100-150° C.; (vi) sintering the immersed support at about 380-500° C. toget a catalyst.
 6. A method for preparation of a selective hydrogenationcatalyst for pyrolysis gasoline according to claim 5 , wherein apromoter is applied to form immersion solution, said promoter beingselected from a group of the VIB or IB elements in the periodical tableof elements.
 7. A method for preparation of a selective hydrogenationcatalyst for pyrolysis gasoline according to claim 5 , wherein ratio ofpromoter and palladium by weight being 0.2˜2:1.